Synthesis of pentafluorides

ABSTRACT

The reactions of uranium, molybdenum, rhenium, osmium and iridium hexafluorides with hydrogen gas in the presence of ultraviolet radiation or with silicon powder in an anhydrous HF slurry provide especially useful, high yield syntheses of pure pentafluorides.

United States Patent 11 1 Asprey et al.

[ Dec. 30, 1975 SYNTHESIS OF PENTAFLUORIDES [75] Inventors: Larned B. Asprey; Robert T. Paine,

Jr., both of Los Alamos, N. Mex.

[73] Assignee: The United States of America as represented by the United States Energy Research and Development Administration, Washington, D.C.

[22] Filed: Mar. 26, 1974 [21 App]. No.: 454,983

521 U.s.c1 204/157.1R 51 int. cu BOIJ 1/10 [58] Field ofSearch..204/l57.l R, DIG. 11,157.111

[56] References Cited UNITED STATES PATENTS 3,l27,334 3/1964 Heffels 204/l57.l R

Primary ExaminerHoward S. Williams Attorney, Agent, or Firm-Dean E. Carlson; Paul D. Gaetjens 57 ABSTRACT 6 Claims, No Drawings SYNTHESIS OF PENTAFLUORIDES BACKGROUND OF THE INVENTION method of partial fluorination of .high'surface area UF at low temperatures with gaseous fluorine-has been used. Heating UF and UF together to yield UF has also been used. These two syntheses suffer from the fact that the methods used in the preparation. of the UF affects its reactivity, and really pure UF from these methods is not readily obtainable. A number of new approaches have been tried. Fluorination of UF in anhydrous HF yields reasonably pure material as does oxidation of UF by UF also in liquid HF. However, both of these methods leave impurities arising from incomplete oxidation of UF or other impurities originally present in the UF Since UF is easily obtainable and can be readily sublimed at room temperature (v.p. z 125 mm), reduction of this should yield UF of high purity providing the reduction does not go beyond UF A method using silicon metal as a reductant with excess UF yields a pure product but the reaction is very slow, circa several days for a few grams. Photolytic reduction of UF using a mercury lamp does yield some UF but very inefficiently and in small yield.

SUMMARY OF THE INVENTION The reduction of uranium, molybdenum, rhenium, osmium and iridium hexafluorides with one equivalent of hydrogen gas in the presence of ultraviolet light from a mercury lamp gives the pentafluoride in excellent purity and is essentially 100% yield. In the reduction of molybdenum, rhenium, osmium and iridium hexafluorides, the rate of reduction is substantially increased in the presence of platinum gauze. The pentafluorides can be freed from the HF produced in the reaction by pumping and condensation of the HF.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Uranium hexafluoride is reacted with hydrogen gas at room temperature in a 30 ml Kel-F tube:

UV UF, HF.

The reaction rate is greatly enhanced by radiation from a low pressure mercury lamp. One gram of UF is completely converted to pure B-UF powder in one day, and the HF produced is easily removed by pumping.

In a second embodiment, UF reacts at room temperature with silicon powder in a stirred anhydrous HF slurry contained in a Kel-F tube according to the reaction:

uF.,+ v. Si day The UF is virtually insoluble in the anhydrous HF, and the SiF, and HF are removed by pumping. One gram of UF is completely converted to pure B-UF powder in 2-3 days. Working in a dry box, the free-flowing B-UF ranging in color from white to yellow-green, is easily recovered from the reaction tubes. Identification is provided by the infrared spectrum of a powder sample held at -l96(crn 623 s,sh, 567 s, 508 s, 405 s, 405 s, sh; and the Raman spectrum of a powder sample held at 23 (Av cm"); 623 s, 610 s, 280 m.'Allattempts to evaporate UF5 from a resistively heated crucible into the ion source of a TOF mass spectrometer resulted in disproportionation of the UF as evidenced by the resulting mass spectrum of UF The B-UF obtained from the above reactions is converted to a a-UF at ca. 120, and the a-UF was identified by x-ray powder diffraction. Attempts were made to carry the chemical reduction from UP to UF by adding additional H or Si, but no. CVIdCIICQfOljlfidUClllOlTbClOW .UF was obtained.

At present, the mechanism of the silicon reduction of UF is not clearly understood, however, we have shown that the production of hydrogen from the reaction of liquid, anhydrous HF and silicon metal is slow compared to the uranium hexafluoride reduction.

A. Molybdenum Pentafluoride tion in anhydrous HF proceeded rapidly to completion in l-2 hours in the presence of platinum gauze. The resulting yellow sublimable solid was characterized by power x-ray diffraction, infrared and Raman spectroscopy and melting point. The data require that the product be MoF The reaction of MoF with H was slow and required irradiation with ultraviolet light. After 3-5 days a good yield of MoF was obtained.

The reaction of MoF with two equivalents of Si metal in HF solution produced a green oil. The oil has been partially characterized and appears to be MoF B. Rhenium Pentafluoride We find that the known reduction of ReF to ReF by W(CO) gives very poor yields and a complex product mixture. On the other hand, we discovered that ReF reacts with one equivalent of silicon (4 ReF ISi) in anhydrous HF solution to give better than yields of a green, sublimable solid established now as ReF by chemical analysis, melting point, and sublimation temperature.

The reduction of rhenium hexafluoride with one equivalent of hydrogen gas using ultraviolet light in the presence of platinum gauze gave essentially 100% yields of rhenium pentafluoride of excellent purity. The compound was characterized by chemical analysis, melting point and sublimation temperature.

C. Osmium Pentafluoride OsF reacts with one equivalent of Si (40sF /Si) in anhydrous HF solution to give better than yields of OsF a yellow-brown solid. The reduction of OsF with one equivalent of hydrogen using ultraviolet light in the presence of platinum gauze also gave OsF in high yield and excellent purity. The osmium pentafluoride was characterized by chemical analysis, mass spectroscopy, x-ray and infrared.

. D. Iridium Pentafluoride The one electron reduction reaction of IrF with both silicon metal and with M has been investigated. The former reaction in HF proceeded rapidly to completion in l-2 hours in the presence of platinum gauze. The product is a yellow sublimable solid which has been characterized by powder x-ray diffraction, infrared and nium, osmium, and iridium hexafluoride, with one equivalent of hydrogen gas in the presence of ultraviolet radiation, at room temperature and for a period of about one day.

2. The method of claim 1 in which the said hexafluoride is reacted in the presence of platinum gauze.

3. The method of claim 2 in which thesaid hexafluoride is rhenium hexafluoride.

4. The method of claim 2 in which the said hexafluoride is iridium hexafluoride.

5. The method of claim 2 in which the said hexafluoride is osmium hexafluoride. I

6. The method of claim 2 in which the said hexafluoride is molybdenum hexafluoride. 

1. A METHOD OF PREPARING PURE PENTAFLUORIDES COMPRISING REACTING AT LEAST ONE OF THE HEXAFLUORIDES SELECTED FROM THE CLASS CONSISTING OF, MOLYBDENUM, RHENIUM, OSMIUM, AND IRIDIUM HEXAFLUORIDE, WITH ONE EQUIVALENT OF HYDROGEN GAS IN THE PRESENCE OF ULTRAVIOLET RADIATION, AT ROOM TEMPERATURE AND FOR A PERIOD OF ABOUT ONE DAY.
 2. The method of claim 1 in which the said hexafluoride is reacted in the presence of platinum gauze.
 3. The method of claim 2 in which the said hexafluoride is rhenium hexafluoride.
 4. The method of claim 2 in which the said hexafluoride is iridium hexafluoride.
 5. The method of claim 2 in which the said hexafluoride is osmium hexafluoride.
 6. The method of claim 2 in which the said hexafluoride is molybdenum hexafluoride. 